For washing and blanching products such as vegetables the produce must be exposed to large quantities of steam for a predetermined time period. The operating cost for blanching is primarily due to the energy expended and the conservation and efficient use of the steam and the prevention of heat loss is of major importance. In many prior devices the conveyor carrying the produce through the blanching chamber passes from the outside atmosphere into the blanching chamber at one end and possibly both ends for receiving and discharging the produce. Naturally such a conveyor serves to conduct heat outside of the chamber thereby requiring more energy to effect the blanching operation. In dry blanching, there is no exposure of the product to water either for washing or cooling. With the introduction of sufficient steam to process the product, the pressure within the blanching chamber is slightly above atomspheric. If the blanching chamber is not sufficiently sealed sufficient steam can escape to result in a significant energy loss.
In addition there sometimes occurs in such apparatus a rapid condensation of the steam resulting in an immediate cooling down of the process usually due to a rapid introduction of cold product. This steam condensation can serve to reduce the pressure in the blanching chamber below atmospheric very rapidly. In some apparatus the seals are formed by lowering the edges of the compartment or hood below the water level in a trough. Any rapid decompression of the compartment, however momentary, can serve to pull air past the sealing water and into the chamber causing undesirable splashing of water and noise in the blanching apparatus due to buckling of the walls of the chamber.
In addition the maintaining of cleanliness in such blanching apparatus is of primary importance and a continual problem. Because of the combination of the produce with the abundance of water, bacteria growth is stimulated. In addition the steam escaping into any surrounding room can cause a bacteria buildup. The present invention improves these prior devices by providing means for solving some of the problems discussed heretofore.